Flexible optical aperture mechanisms
a flexible, optical aperture technology, applied in the direction of optics, optical elements, instruments, etc., can solve the problems of limited number of types of shapes that can be accessed on the linear slider or the tape drive, and limited aperture shap
Active Publication Date: 2017-05-09
KLA CORP
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Benefits of technology
This patent describes a system and method for combining multiple optical apertures in an optical inspection system. The apertures can have different shapes and can be positioned in a stacked configuration along an optical beam path. This enables the combined optical aperture shape to be customized for different inspection needs. The system can include sheets of optical apertures with different shapes that can be moved and aligned to provide the desired inspection configuration. The technical effect is the ability to create a customizable, combined optical aperture shape for better inspection of optical components.
Problems solved by technology
The shape of the aperture, however, is limited (e.g., typically the blades create an aperture approximating a circular aperture) and there is no allowance for the inclusion of optical elements in the iris mechanism.
The number of types of shapes that can be accessed on the wheel, however, is limited by the apertures on the wheel.
Similar to the aperture wheel, the number of types of shapes that can be accessed on the linear slider or the tape drive, however, is limited by the apertures on the slider or the tape drive.
Liquid crystal arrays, however, do not allow full open transmission or full blocking of light, which leads to inefficiency and / or light leakage.
Liquid crystal arrays also cause stray light and / or scatter light, cause optical aberrations, and may provide poor transmission and / or limited lifetime at short wavelengths (e.g., UV, DUV, and VUV).
Tilt mirror arrays, however, do not allow full open transmission, which causes inefficiency.
In addition, tilt mirror arrays can cause stray or scattered light, cause optical aberrations, and / or can have limitations on light power density or contamination with DUV light.
Tilt mirror arrays also may not allow efficient incorporation of shapes with spectral, polarizing, or phase properties.
Photofilm systems, however, do not allow fully open and fully blocked transmission, require time for exposure and development, and have a low damage threshold.
Photofilm systems may also degrade and cause contamination when used with UV, DUV, or VUV light systems and may not allow efficient incorporation of shapes with spectral, polarizing, or phase properties.
Inkjet printing systems, however, does not allow full open transmission and requires substrate recleaning or a consummable substrate.
Inkjet printing systems may also have a low damage threshold and degrade or cause contamination when used with UV, DUV, or VUV light systems.
Inkjet printing systems also may not allow efficient incorporation of shapes with spectral, polarizing, or phase properties.
Fourier filters, however, allow for very few shapes and are only mostly useful to block diffraction patterns.
Microshutter arrays, however, may not allow full open transmission due to the array structure and the array structure may cause stray light.
Microshutters are also complex in nature which can add cost and reduce reliability.
As described above, previous flexible optical aperture systems have several disadvantages including, but not limited to, disadvantages such as optical transmission losses, incomplete optical blocking, straylight, optical aberrations, limited shape flexibility or spatial resolution, low damage threshold and DUV incompatibility, limited flexibility to incorporate additional optical features (such as apodization, phase plates, shaped polarizers, and spectral apertures), and incompatibility with existing optical systems.
In addition, the flexible optical aperture systems and methods may have a high damage threshold and compatibility with various optical systems (e.g., UV, DUV, VUV, and EUV optics).
Method used
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[0042]In the context of this patent, the term “coupled” means either a direct connection or an indirect connection (e.g., one or more intervening connections) between one or more objects or components. The phrase “directly connected” means a direct connection between objects or components such that the objects or components are connected directly to each other so that the objects or components operate in a “point of use” manner.
[0043]Optical inspection systems (e.g., optical wafer inspection systems) may use optical apertures to define illumination and imaging paths in the optical inspection systems. While embodiments described herein are directed to providing optical apertures in optical wafer inspection systems, it is to be understood that the embodiments described may also be useful in other optical inspection and / or metrology systems. Examples of other optical systems include, but are not limited to, optical wafer metrology systems, optical mask inspection and metrology systems,...
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A system for providing flexible optical aperture shapes in an optical inspection system (e.g., an optical wafer inspection system) is described. The system includes one or more mechanisms for providing multiple optical aperture shapes along an optical beam path in the optical wafer inspection system. The multiple optical apertures shapes are stacked or overlapped to combine the shapes and form a single combined optical aperture shape along the optical beam path.
Description
PRIORITY CLAIM[0001]This patent claims priority to U.S. Provisional Patent Application No. 61 / 738,352 filed Dec. 17, 2012, which is incorporated by reference in its entirety.BACKGROUND[0002]1. Field of the Invention[0003]The present invention relates to optical wafer inspection systems. More particularly, the invention relates to apertures and shaping of the imaging path in optical wafer inspection systems.[0004]2. Description of Related Art[0005]Optical apertures with flexible sizes and / or shapes are useful in manipulating illumination and imaging properties in optical wafer inspection systems. Optical apertures with such flexibility allow illumination and imaging properties to be optimized given a selected wafer pattern and / or selected types of defects of interest. Varying sizes and shapes of optical apertures can be applied in both brightfield and darkfield optical modes. The use of special aperture sizes and / or shapes are also known to enhance signal to noise ratios in optical w...
Claims
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IPC IPC(8): G02B5/00G02B26/06G02B26/02
CPCG02B5/005G02B26/02G02B26/06
InventorBRUNNER, RUDOLF
OwnerKLA CORP